Hydrazine

ABSTRACT

HYDRAZINE IS PREPARED FROM KETAZINES BY FEEDING A KETAZINE AND WATER TO A FRACTIONATING COLUMN WHEREIN THE KETAZINE IS MISCIBLE WITH WATER TO ONLY A LIMITED EXTENT. THE COLUMN IS OPERATED AT ELEVATED TEMPERATURE AND AT SUPERATMOSPHERIC PRESSURE AND HAS A ZONE IN THE VICINITY OF THE POINT OF INTRODUCTION OF THE MATERIALS WHEREIN THE RESIDENCE TIME IS RELATIVELY LARGE IN THIS ZONE AS COMPARED WITH THE REMAINDER OF THE COLUMN. AN AQUEOUS SOLUTION OF HYDRAZINE IS REMOVED AS BOTTOMS.

United States Patent [56] References Cited UNITED STATES PATENTS3,189,411 6/1965 Kohnen et a1 23/190 3,151,046 9/1964 Larson 202/158Primary Examiner-Earl C. Thomas Assistant Examiner-Hoke S. MillerAttorney-Richard P. Crowley ABSTRACT: Hydrazine is prepared fromketazines by feeding a ketazine and water to a fractionating columnwherein the ketazine is miscible with water to only a limited extent.The column is operated at elevated temperature and at superatmosphericpressure and has a zone in the vicinity of the point of introduction ofthe materials wherein the residence time is relatively large in thiszone as compared with the remainder of the column. An aqueous solutionof hydrazine is removed as bottoms.

PATENTED SEP21 IHYI INVENTORS STEPILBQ ROBERT MERCER ELLIS BRIAN JOHNNEEDHAM 1 ATTORNEY HYDRAZHNE The present invention relates to a processfor preparing hydrazine from ketazines which are miscible with wateronly to a limited extent.

it is possible to form hydrazine by hydrolysis of water-soluble acetoneazine in aqueous solution at elevated temperature and ressures, thehydrolysis being conveniently effected on the trays of a fractioningcolumn operated under pressure. Upon hydrolysis of ketazines, hydrazoneand ketone are formed and hydrazine may be obtained bydisproportionation of the hydrazone to hydrazine and the azine. Thehydrolysis step involves handling a two-phase liquid system where theketazines are miscible with water only to a limited extent andsurprisingly it has been found possible to handle such a twophase liquidsystem if the residence time of the mixture which is fed to the columnis relatively long in a zone in the vicinity of the point of feed of themixture to the column prepared with the residence times in similarlengths of other parts of the column.

Accordingly the present invention is for a process for preparinghydrazine which comprises feeding a ketazine which is miscible withwater only to a limited extent, such as methyl ethyl ketazine, and waterto a distillation column operated at an elevated temperature and at asuperatmospheric pressure, a zone in the vicinity of the point of feedof the ketazine to the column having plates so designed that theresidence time thereof is relatively long compared with the re sidencetimes of plates or packing equivalent thereto outside this zone in otherparts of the column and recovering an aqueous solution of hydrazine asbottoms.

Preferably 1 to 4 parts by weight of water are fed to the column forevery part by weight of ketazine.

In the zone in the vicinity of the ketazine feed, the ketazine ishydrolized to hydrazone, the presence of which increases the solubilityof the ketazine thereby increasing its rate of hydrolysis. Below thiszone hydrazone is disproportionated to azine and hydrazine, the azinebeing returned to the zone in the vicinity of the ketazine/water feedand hydrazine being recovered from the sump. In the zone above theketazine/water feed zone unhydrolysed ketazine is condensed and returnedto the ketazine/water feed zone and ketone/water is distilled off.

The present invention is also for a fractionating column wherein traysin the vicinity of the feed inlet(s) to the column, have a greaterresidence time than each of the trays or packing equivalent thereto inthe remainder of the column.

It is preferred to operate the column at a temperature in the range 150to 200 C. and at a pressure in the range 2 to 25 atmospheres aboveatmospheric pressure.

in operating the process of the present invention the ketazine isconverted to the ketone and hydrazine the ketone being removed asdistillate and hydrazine being removed as bottoms.

The ketazine and water may be fed to the distillation column at the samepoint or at different points. If the feeds are at different points theketazine is preferably fed at a point below that at which the water isfed to the column. 1f the ketazine and water are fed at the same pointthey may be mixed before feeding. Preferably the feeds are heated beforebeing fed to the column for example to a temperature in the range 60 to160 C.

Suitably the zone in the vicinity of the point of feed of the ketazineto the column is equivalent to 2-7 theoretical trays, preferably 3-5theoretical plates, the zone below the ketazine feed zone is equivalentto 3-15 theoretical plates, preferably 5-10 theoretical plates, and thezone above the ketazine feed zone is equivalent to 3-15 theoreticalplates preferably 5-12 theoretical plates. Desirably the zone in thevicinity of the point of feed of the ketazine to the column contains 2-6actual high-residence-type trays having an overall residence time of3-15 minutes. Preferably the zone in the vicinity of the point of feedof ketazine contains two or three highresidence-type trays immediatelybelow the point of feed and one or two highresidence-type traysimmediately above the point of feed.

residence time. Ketazine and water are fed to column 1 through line 4and ketone and water are removed through line 5. l-lydrazine and waterare removed from the sump through line 6.

The following example is given to illustrate the process of the presentinvention.

EXAMPLE A column 9 inches in diameter was packed with knitmesh exceptfor the middle section which consisted of three high-residence-typetrays. The liquid holdup of each of these high 'high-residence-typetrays was approximately 250 cubic inches.

The column was operated at a reflux ratio of 4:1 a pressure of poundsper square inch gauge and a sump temperature of 180 C. Methyl ethylketone azine (43.5 pounds per hour) and water (1 11 pounds per hour)were heated to C. and fed to the middle plate of the hydrolysis section.Methyl ethyl ketone (44.1 pounds per hour), water (14.9 pounds per hour)and methyl ethyl ketone azine (0.6 pounds per hour) were removed fromthe top of the column whilst hydrazine (9.80 pounds per hour), water(85.4 pounds per hour) and methyl ethyl ketone (0.11 pounds per hour)were continuously withdrawn from the sump.

We claim:

11. A process for the preparation of hydrazine by the fractionaldistillation of a ketazine at an elevated temperature and at asuperatmospheric pressure sufficient to hydrolyze the ketazine in ahydrolyzing zone, which process comprises;

a. feeding water and the ketazine which forms a two-phase liquid systeminto a hydrolyzing zone, the hydrolyzing zone characterized in that theresidence time of the ketazine and water is relatively long comparedwith the residence times outside of the hydrolyzing zone;

b. hydrolyzing the ketazine in the hydrolyzing zone to hydrazone, thepresence of which hydrazone increases the solubility of the ketazine insaid zone, thereby increas ing its rate of hydrolysis in the hydrolyzingzone;

0. fractionating the hydrazone so formed in a zone below the hydrolyzingzone to azine and hydrazine; and

d. recovering an aqueous solution of hydrazine.

2. The process as claimed in claim 11 which includes operating at atemperature in the range 150 to 200 C.

3. The process as claimed in claim 1 which includes maintaining apressure in the range of 2 to 25 atmospheres.

4. The process as claimed in claim 1 which includes feeding the ketazineand water at separate points, the ketazine feed point being below thewater feed point.

5. The process as claimed in claim 1 which includes mixing the water andthe ketazine before being fed to the hydrolyzing zone.

6. The process as claimed in claim 1 which includes heating the waterand the ketazine before being fed to the hydrolyzing zone.

7. The process as claimed in claim 6 which includes heating the waterand the ketazine to a temperature in the range 60 to C.

8. The process as claimed in claim 1 wherein the zone in the vicinity ofthe point of feed of the ketazine is equivalent to about 2-7 theoreticalplates and the zones above and below the ketazine feed zone are eachequivalent to about 3-15 theoretical plates.

9. The process as claimed in claim 1 wherein the zone at the point offeed of the ketazine contains 2-3 high-residence-type trays immediatelybelow the point of feed and 1-2 high-residence-type trays immediatelyabove the point of feed.

10. The process as claimed in claim 1 which includes providing arelatively long residence time in the hydrolyzing zone for the feedstream by a plurality of distillation trays in the hydrolyzing zone withrelatively high weirs in respect to distillationtrays outside of thezone having relatively low want.

11. The process as claimed in claim 1 which includes providing aplurality of high liquid-residence fractionating trays in thehydrolyzing zone and packing material in the other zones.

12. The process as claimed in claim 1 which includes feeding about 1 to4 parts by weight of water for every part by weight of the ketazine.

13. The process as claimed in claim 1 which includes recovering aketone, and recovering the unhydrolyzed ketazine from the zone above thehydrolyzing zone, condensing the ketazine so recovered and returning theketazine to the hydrolyzing zone.

14. A process for the preparation of hydrazine by the fractionaldistillation of methylethyl ketazine in a distillation column in ahydrolyzing zone, which process comprises:

a. feeding methylethyl ketazine and water in a ratio of about 1 to ,4parts of water for every part of methylethyl ketazine into a hydrolyzingzone located intermediate in a distillation column, the hydrolyzing zoneso designed that the residence time of the ketazine is relatively longcompared with the residence times of the ketazine above and below thezone, the water and ketazine heated to a temperature in the range ofabout 60 to 160 C., the process operated at a temperature in the rangeof to 200 C., and a pressure of about 2 to 25 atmospheres;

b. hydrolyzing the methylethyl ketazine in the hydrolyzing zone tomethylethyl hydrazone, the presence of which hydrazone increases thesolubility of the methylethyl ketazine in the zone;

c. fractionating the methylethyl hydrazone to the azine and hydrazine;

d. recovering an aqueous solution of hydrazine; and

e. distilling off and recovering methylethyl ketone.

15. The process as claimed in claim 14 which includes feed ing thereofthe methylethyl ketazine and water into the hydrolyzingzone at separatepoints, the methylethyl ketazine feed point being below the water feedpoint.

16. The process as claimed in claim 14 which includes mixing the waterand methylethyl ketazine before being fed to the hydrolyzing zone.

17. The process as claimed in claim 14 which includes providing aplurality of high-liquid-residence fractionating trays in thehydrolyzing zone and packing material in the other zones.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 s 607s 04] Dated September 2] 9 1 97] Inventor) Stephen Robert Mercer E1 1 isand Brian John Needham It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In the heading to the printed specification, identification of theserial number --App1n. No. 765,598-- has been omitted; line 8,"Laughborough" shouid read --Loughborough--.

Signed and sealed this lLpth day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. The process as claimed in claim 1 which includes operating at atemperature in The range 150* to 200* C.
 3. The process as claimed inclaim 1 which includes maintaining a pressure in the range of 2 to 25atmospheres.
 4. The process as claimed in claim 1 which includes feedingthe ketazine and water at separate points, the ketazine feed point beingbelow the water feed point.
 5. The process as claimed in claim 1 whichincludes mixing the water and the ketazine before being fed to thehydrolyzing zone.
 6. The process as claimed in claim 1 which includesheating the water and the ketazine before being fed to the hydrolyzingzone.
 7. The process as claimed in claim 6 which includes heating thewater and the ketazine to a temperature in the range 60* to 160* C. 8.The process as claimed in claim 1 wherein the zone in the vicinity ofthe point of feed of the ketazine is equivalent to about 2-7 theoreticalplates and the zones above and below the ketazine feed zone are eachequivalent to about 3-15 theoretical plates.
 9. The process as claimedin claim 1 wherein the zone at the point of feed of the ketazinecontains 2-3 high-residence-type trays immediately below the point offeed and 1-2 high-residence-type trays immediately above the point offeed.
 10. The process as claimed in claim 1 which includes providing arelatively long residence time in the hydrolyzing zone for the feedstream by a plurality of distillation trays in the hydrolyzing zone withrelatively high weirs in respect to distillation trays outside of thezone having relatively low weirs.
 11. The process as claimed in claim 1which includes providing a plurality of high liquid-residencefractionating trays in the hydrolyzing zone and packing material in theother zones.
 12. The process as claimed in claim 1 which includesfeeding about 1 to 4 parts by weight of water for every part by weightof the ketazine.
 13. The process as claimed in claim 1 which includesrecovering a ketone, and recovering the unhydrolyzed ketazine from thezone above the hydrolyzing zone, condensing the ketazine so recoveredand returning the ketazine to the hydrolyzing zone.
 14. A process forthe preparation of hydrazine by the fractional distillation ofmethylethyl ketazine in a distillation column in a hydrolyzing zone,which process comprises: a. feeding methylethyl ketazine and water in aratio of about 1 to 4 parts of water for every part of methylethylketazine into a hydrolyzing zone located intermediate in a distillationcolumn, the hydrolyzing zone so designed that the residence time of theketazine is relatively long compared with the residence times of theketazine above and below the zone, the water and ketazine heated to atemperature in the range of about 60 to 160* C., the process operated ata temperature in the range of 150* to 200* C., and a pressure of about 2to 25 atmospheres; b. hydrolyzing the methylethyl ketazine in thehydrolyzing zone to methylethyl hydrazone, the presence of whichhydrazone increases the solubility of the methylethyl ketazine in thezone; c. fractionating the methylethyl hydrazone to the azine andhydrazine; d. recovering an aqueous solution of hydrazine; and e.distilling off and recovering methylethyl ketone.
 15. The process asclaimed in claim 14 which includes feeding thereof the methylethylketazine and water into the hydrolyzing zone at separate points, themethylethyl ketazine feed point being below the water feed point. 16.The process as claimed in claim 14 which includes mixing the water andmethylethyl ketazine before being fed to the hydrolyzing zone.
 17. Theprocess as claimed in claim 14 which includes providing a plurality ofhigh-liquid-residence fractionating trays in the hydrolyzing zone andpacking material in the other zones.